[postcss][postcss]-filter-plugins ![Build Status][ci]

> Exclude/warn on duplicated PostCSS plugins.

Install

With npm do:

``console
$ npm install postcss-filter-plugins --save
`

Example

Note that this plugin does not actually transform your CSS; instead, it ensures
that plugins in the PostCSS instance are not duplicated. It is intended to be
used by plugin packs such as [cssnano] or [cssnext].

`js
var counter = postcss.plugin('counter', function () {
return function (css) {
css.eachDecl('foo', function (decl) {
let value = parseInt(decl.value, 10);
value += 1;
decl.value = String(value);
});
}
});

var css = 'h1 { foo: 1 }';
var out = postcss([
filter(),
counter(),
counter()
]).process(css).css;

console.log(out);
// => h1 { foo: 2 }
// Note that you will get a PostCSS warning in the message registry
`

API

$3

#### options

##### direction

Type: string
Default: 'both'

Pass 'forward', 'backward', or 'both' to customise the direction in which the
plugin will look in the plugins array. See the [tests] for examples on how this
works.

`js
postcss([ filter({
direction: 'forward'
}) ]).process(css).css);
`

##### exclude

Type: array
Default: [] (empty)

Plugins that should be excluded from the filter. Pass an array of plugin names.

`js
postcss([ filter({
exclude: ['postcss-cssstats']
}) ]).process(css).css);
`

##### silent

Type: boolean
Default: false

Set this to true to disable the plugin from emitting any PostCSS warnings.

`js
postcss([ filter({
silent: true
}) ]).process(css).css);
`

##### template

Type: function
Default: format function

This function will be passed each PostCSS plugin object. You are expected to
return a string from each call, which is then used to warn the user about her
duplicated plugins.

`js
postcss([ filter({
template: function (plugin) {
return 'Duplicate plugin found: ' + plugin.postcssPlugin;
}
}) ]).process(css).css);
``

Usage

See the PostCSS documentation for
examples for your environment.

Contributors

Thanks goes to these wonderful people (emoji key):

|
_{Ben Briggs}
💻 📖 👀 ⚠️ |
_{Maxime Thirouin}
📖 |
_{Andreas Lind}
💻 |
| :---: | :---: | :---: |

This project follows the all-contributors specification.
Contributions of any kind welcome!

License

MIT © Ben Briggs

[ci]: https://travis-ci.org/postcss/postcss-filter-plugins
[cssnano]: http://cssnano.co
[cssnext]: http://cssnext.io
[postcss]: https://github.com/postcss/postcss
[tests]: src/__tests__